الفهرس 
AcknowledgementOnly 14 pages are availabe for public view
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Abstract
Fortunately, a functionally graded piston as a direct application was successfully fabricated using a simple new mechanical mechanism with two aluminum alloys A242 and A336. The vertical centrifugal apparatus was taken in mind to refine the microstructure for the cast specimen piston. Three types of samples were the main target to study as a piston of A242 that has a low silicon percentage (0.1 Wt %) and another specimen of A336 with a higher silicon content (12 Wt %). The last specimen type was the vital one that had the FGM principle. A chemical analysis test was performed in the basis of spectroscopy to the three types of piston to ensure that the required gradient was done. The two samples- A242 and A336-had no changes in their internal ingredient percentages axially along the head the piston to its skirt. But the FGM had a great result of about 11.98 wt % of silicon starting from the piston head. Descending to the piston skirt, the silicon content was decreasing till the skirt region having a value of about 1.5 wt %. Another six readings were taken in between to ensure the gradient manner that was normally found. Copper content had a nice reverse relation with the silicon content. Copper started with 0.789 wt% at the piston head and was increasing axially through the piston till it reached the skirt with a value of 3.15 wt%. Also, magnesium had its own gradient as the same slope direction of copper. Magnesium started with 0.788 wt% at the piston head and was increasing slightly till it reached the skirt with a value of 1.24 wt%. Nickle had slightly differences with an average value of 2.512 wt% axially along the piston from the head to the skirt. A hardness test was done to study the effect of the gradient existed that was proved by the previous test. Every specimen was sliced to a thin tetragonal sample. The two slices A242 and A336 had many readings till accurate averages for hardness values as 102.733 HV for A336 and 74.33 HV for A242 were calculated. The FGM slice had nine readings axially from the skirt region to the head of the slice. The hardness scored a value of 72.2 HV that was increasing axially towards the head region of the piston slice till it reached the maximum value of 93.1 HV. Wear test was done also to see the effect of the gradient existed. Test was done according to ASTM G99 with a pin-disk test. The wear was calculated in the basis of the weight loss. The wear was calculated for the pin and the steel disk for the three specimen types. Small pins were cut off from the piston specimen to be able to do the wear test. Wear test was repeated for four times to get accurate averages. Weight loss at pins for A242 and A336 was 1.441 and 1.082 respectively. Weight loss at the disk for A242 and A336 was 0.00306 and 0.00038 respectively. The FGM pins recorded a value of 1.203 at the head region of the piston, meanwhile recording a value of 1.778 at the skirt region. Through the previous wear test, Coefficient of friction was calculated for all the specimens. Coefficient of friction for A242 and A336 recorded 0.3285 and 0.2615 respectively. The FGM sample had Coefficient of friction of 0.244 at region of the piston head for the pins tested and was increasing axially towards the skirt region with a maximum value of 0.384 that showed that the top part of the sample was more wear resistant than the skirt part. These tests are supporting each other towards the FGM piston cast showing a successful gradient distribution that will help to extend the piston lifetime that was the target from the beginning.